It is known to produce colored photographic images by means of multilayer silver halide materials comprising a support having coated thereon a red-sensitive, a green-sensitive and a blue-sensitive silver halide emulsion layer, each of said silver halide emulsion layers having associated therewith non-diffusing color couplers for the production, respectively, of the cyan, magenta and yellow images. Usually, color photographic materials also contain other layers, for example a yellow filter layer, an anti-halation layer, intermediate layers and protective layers.
It is also known to produce colored photographic images by using multilayer materials in which at least two silver halide emulsion layers are respectively provided for producing one or more of the three different color images. British Pat. No. 818,687 suggests increasing the sensitivity of a multilayer color material by using at least one emulsion layer which comprises two component silver halide emulsion layers (hemi-layers) sensitized to the same spectral region, of which the upper component layer (most sensitive layer) has a sensitivity higher than that of the bottom layer (least sensitive layer). British Pat. No. 923,045 suggests the use of double layers of different sensitivity, of which the more sensitive layer produces the lower color density during color development. In this way, it is possible to increase sensitivity without at the same time adversely affecting graininess.
U.S. Pat. No. 3,843,369 discloses how the graininess of a color image can be improved by using three different silver halide emulsion component layers having the same spectral sensitivity, but different general sensitivity decreasing in the order from the upper (most sensitive) component emulsion layer to the intermediate (medium sensitivity) component emulsion layer and to the bottom (least sensitive) component emulsion layer. It is preferred that, in the intermediate and upper component layer, a maximum color density of at most 0.6 is obtained. The maximum color density may be controlled for instance by reducing the coupler content, i.e. by increasing the silver halide to coupler ratio. In higher sensitive color negative materials, triple layers are particularly useful for forming the magenta color image, owing to the fact that the sensitivity of the human eye is the highest in the green spectral region, so that the graininess of the magenta color image is most noticeable.
Finally, British Pat. No. 1,576,991 discloses a color photographic material in which the more sensitive component layer of a double red-sensitive silver halide emulsion layer is arranged between two component layers of a triple green-sensitive silver halide layer. In comparison with a color photographic material of U.S. Pat. No. 3,843,369 (comprising, in order, two red-sensitive silver halide emulsion layers of different sensitivities and three green-sensitive silver halide emulsion layers of different sensitivities. No layer of one color sensitivity is between two silver halide layers having the same second color sensitivity.) color photographic material of British Pat. No. 1,576,991 provides a higher sensitivity of the cyan image with substantially the same color graininess, without increasing the sensitivity of the other image layers.
Despite the numerous efforts made, there is still the need to find special layer arrangements in color photographic materials to obtain the extremely high sensitive photographic elements required by the photographic market.